The poultry industry is one of the fastest growing segments of the animal industry. More than 50 billion chickens are raised annually as a source of food, for both their meat and their eggs. About 75 percent of the world's poultry meat, and 68 percent of eggs are produced in ways that are described as intensive.
In this industry, the handling of wasted or bad eggs represents a serious logistical and environmental problem. Wasted eggs arise from different sources: eggs that do not meet the standards for human consumption (too big or too small, contaminated, etc), eggs from incubator farms (hatcheries) that fail developing chickens, eggs that are not sold and pass their “best before” date, etc. These wasted eggs are difficult to transport and handle.
Animal by-products not intended for human consumption are a potential source of risks to public and animal health. Wasted eggs are considered a “Category 3” under European regulation 1069/2009 laying down health rules as regards animal by-products and derived products not intended for human consumption. This means that wasted eggs can be disposed of by various means, including processing in a plant approved to handle it, use in the manufacture of pet food, in the oleochemical industry or in the manufacture of technical products such as fertilizer. But it cannot be disposed in a landfill, because it would lead to unsustainable costs and risks for the environment. Therefore the processing of wasted eggs is highly desirable.
In a commonly used process, eggs are broken to separate the shell, and the resulting liquid is pasteurized, concentrated and spray dried to generate “egg powder”, suitable for consumption or animal feed. In this process it is important that the egg does not coagulate, since the powder egg must retain its functional characteristics and be able to regenerate egg or an egg-like product upon moisturizing.
Although making powder egg via spray drying would be a possible solution for handling eggs that should be discarded, such a process is expensive for waste material and cannot be used for economical reasons.
GB 102,815 describes the processing of wasted eggs for the manufacture of foodstuff for animals or poultry. Eggs are broken, heated in a drier to 115° C. with the addition of preservatives, and ground.
U.S. Pat. No. 3,778,425 discloses a process for the manufacture of granular or powdery purified whole egg protein by heating in the presence of solvents such as alcohol forming coagulated egg proteins which are contacted with water to remove carbohydrates and inorganic salts, and then a solvent to remove fat. The protein substance is dried to form a granular product, useful as protein source, animal feed or food supplement.
JP2007222074 describes a process to prepare animal feed from eggs, using a grinder, heating machine, a dryer, a grinder and a sieve. The shell is not separated.
U.S. Pat. No. 6,348,223 describes a milk replacer product made from inedible egg product. The process includes separation of the shell, refrigerating the liquid egg to 7° C. or less, heat-pasteurizing at 60° C. for at least 4.5 minutes and packaging to produce a liquid product or spray drying to generate egg powder.
U.S. Pat. No. 4,511,589 discloses a process for the continuous pasteurization of eggs characterized in that liquid egg material is passed under operating pressure through a first scraped surface heat exchanger to raise the temperature of the egg material to the pasteurization temperature, after which it is passed to a heated holding vessel under pressure of a sterile inert gas for a period of time which ensures pasteurization but which is sufficiently short to ensure that substantially no coagulation occurs, and finally through a second scraped surface heat exchanger where it is cooled to a temperature below 10° C. over a period of time less than 5 minutes. The scraped surface heat exchangers avoid problems with the flowability and high viscosity of the eggs, but coagulation is avoided.
US 2005/0287260 refers to a method for extending the shelf life of egg products. This method comprises pasteurizing egg material and treating the pasteurized egg material with pressure. Acidifying agents may be added to the egg material before or after pasteurization.
KR 20090107833 discloses a method of preparing egg fermentation food to extend the shelf life of egg. Egg liquid is fermented using Aspergillus sp. and then coagulated.
There still remains the need for a process to process wasted eggs in a simple and economic way, able to solve the problems coagulation can cause in the handling equipment, and converting the wasted eggs in a valuable material.